Methods for measuring electrochemiluminescent phenomena have been known for some years. Such methods make use of the ability of special metal complexes to achieve, by means of oxidation, an excited state from which they decay to ground state, emitting electrochemiluminescence. For review see Richter, M. M., Chem. Rev. 104 (2004) 3003-3036.
At this time, there are a number of commercially available instruments that utilize electrochemiluminescence (ECL) for analytical measurements. Species that can be induced to emit ECL (ECL-active species) have been used as ECL labels. Examples of ECL labels include organometallic compounds such as the tris-bipyridyl-ruthenium (RuBpy) moiety where the metal is from, for example, the metals of group VII and VIII, including Re, Ru, Ir and Os. Species that react with the ECL label in the ECL process are referred to herein as ECL coreactants. Commonly used coreactants for ECL include tertiary amines (e.g., tripropylamine (TPA)), oxalate, and persulfate. The light is generated by ECL labels or ligands; the participation of the binding reagent in a binding interaction can be monitored by measuring ECL emitted from the ECL label. Alternatively, the ECL signal from an ECL-active compound may be indicative of the chemical environment (see, e.g., U.S. Pat. Nos. 5,641,623 and 5,643,713, which describes ECL assays that monitor the presence or destruction of special ECL coreactants). For more background on ECL, ECL labels, ECL assays and instrumentation for conducting ECL assays see U.S. Pat. Nos. 5,093,268; 5,147,806; 5,240,863; 5,308,754; 5,324,457; 5,591,581; 5,597,910; 5,679,519; 5,705,402; 5,731,147; 5,786,141; 5,846,485; 5,866,434; 6,066,448; 6,136,268 and 6,207,369, and European Pat. No. 0 441 875, and Int. Pat. Appln. Pub. Nos. WO 97/36931; WO 98/12539; WO 99/14599; WO 99/32662; WO 99/58962; WO 99/63347; WO 00/03233 and WO 98/57154.
Commercially available ECL instruments have demonstrated exceptional performance. They have become widely used for reasons including their excellent sensitivity, dynamic range, precision, and tolerance of complex sample matrices. The commercially available instrumentation uses flow cell-based designs with permanent reusable flow cells.
Available sample volumes for the determination of analytes are often limited and more and more different analytes have to be determined out of one sample. Also the development of faster laboratory equipment for assay automation and more sensitive methods for the detection of analytes are required. This leads to the need for high sensitive and specific electrochemiluminescent assays and methods for performing them. In addition, improvements associated with safety hazards or environmental concerns should be considered.
However, even more sensitive detection of analytes would be of great advantage. Thus, the present methods may provide improvements over known methods and reagent compositions, especially with respect to enhancement of the ECL signal and an improved analyte detection in combination with electrochemiluminescent procedures. It would be desirable to find novel signal enhancing reagents and/or compounds with improved performance in electrochemiluminescent assays.